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If you think you already spend too much time checking your Facebook notifications, wait until it starts beeping at you.

The social network is testing out a new sound alert system that makes a "ding dong'' noise every time someone writes on your timeline, sends you a message or invites you to an event.

The unpublicized experiment was uncovered this week by a reporter for technology blog Venturebeat, whose Facebook profile was one of the few involved in the trial.

Facebook today confirmed to News Ltd that only a small number of profiles had been enabled with the new sound alerts, which can be controlled through account settings, however the idea is already being slammed online by annoyed users.

"Seriously, the Facebook inbox alert sound should go,'' tweeted @evanspughe. On tech website Mashable one user commented "Let's take an already annoying product, Facebook, and make it more annoying with noises. Way to go there, Zuck.''

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A YouTube video demonstrating the sound alert in action has also attracted a number of irritated comments from Facebook users.

"NO? Bad, Facebook!'' wrote IceFurnace.

"Just as long as we can use our own or mute it,'' wrote ShylockAkita.

The trial comes as Facebook also experiments with a revamp of its comments system which will allow users to "reply'' to comments made on timeline posts.

"We are testing a new way to add comments to a post on Facebook,'' a Facebook spokesperson told News Ltd. "Now you will be able to reply to another comment as well as the original post.''

Read more tech news and reviews at News.com.au.